No problem to run TPB site on my end. So, how do I know that Opera blocks mining? I received no pop up, notice, warning etc. I would like to get proof that Opera is indeed blocking mining sites. Opera is boasting with this feature so I would expect a clear message to users how to check it and to get proof of its efficiency.

@pe73 i tried the nocoin add-on back when it came out and it does work, but i started using cryptostop add-on instead simply because it provided a little popup that indicated mining scripts were stopped and displayed a little number. I guess for convenience the adding of a little popup would be appreciated.

You have to open the Developer Tools → Sources tab to see the mining web workers. They will be named like "#1", "#2" etc. with small gear icons next to them.
What NoCoin does is that it closes them before they could work, and the website reopens them - it's an infinite fight.

Just look at Opera's CPU use in the Task Manager and you should see.

Unfortunately NoCoin doesn't seem to work for ThePirateBay's WASM (assembly) scripts at the moment.

... Developers will have to come up with a smarter solution. A popup etc.

Actually, the popup idea would be useful to alert users to what is going on with that website's code or the JavaScripted site calls it invokes (ads, etc). The users then could/should each raise %$#/@ with the original site operators to get their act together, and in the meantime (or if the site persists in it) the user could avoid the site like the plague.